Due to illness, the pumping function of a heart can be reduced, which is also called cardiac insufficiency. Cardiac insufficiency is from the medical as well as from the economical standpoint of great and increasing importance. In the second decade of this century, 23 million people worldwide will suffer from cardiac insufficiency; the annual rate of new cases will be about 2 million people. In the US alone, 5 million people are currently suffering from cardiac insufficiency. Here, the annual rate of new cases is approximately 550,000 people. Already in this decade, the number of incidences in people over 50 years of age will double to more than 10 million. The same applies to the European continent.
Causes for cardiac insufficiency can be impaired contractility or reduced filling of the cardiac chambers due to damage to the myocardium. Hypertension can lead to an increased pumping resistance, which can also negatively affect the pumping function of the heart. The pumping function of a heart can also be reduced by leaking valves (e.g., a leaking aortic valve or mitral valve). Impairments of the cardiac conduction system generate arrhythmias, which can also lead to a reduced pumping function of the heart. If the movement of the heart is restricted from the outside, e.g., due to an accumulation of fluid in the pericardium, this can result in a reduced pumping function as well. Cardiac insufficiency often leads to shortness of breath (especially in the case of left ventricular insufficiency), or to water retention in the lungs or in the abdomen (in particular in the case of right ventricular insufficiency).
Different types of cardiac insufficiencies are treatable with medication or surgery. In some cases of arrhythmias, normal cardiac rhythm can be restored with a pacemaker. A leaking valve can be replaced surgically with a cardiac valvular prosthesis. A reduced pumping function can be assisted by an implanted heart pump. A treatment approach addressing the various causes of heart insufficiency is to assist the pumping function of the heart by means of an implant, which exerts mechanical pressure onto the heart and therefore improves its pumping performance.
Some known mechanical ventricular assist devices have been disclosed in U.S. Pat. No. 5,749,839 B1 and U.S. Pat. No. 6,626,821 B1, and in WO application 00/25842. These documents disclose mechanical ventricular assist devices that require open-chest surgery. Many cardiac assist systems are complex and can only be implanted by means of an elaborate surgical procedure. All cardiac assist systems are integrated into the blood circulation of the patients. Improved centrifugal or magnetically supported impeller systems carry blood continuously. The contact of the blood with the surface of the implanted systems poses a great engineering and medical challenge. Common complications of cardiac assist systems are strokes, hemorrhage and septicemia. They often lead to long-term hospitalization and frequent re-admissions of patients already released from the hospital.